Encyclopedia

The making of parts and products using a computer-driven, additive process, one layer at a time. 3D printing builds parts out of plastic, metal and other materials directly from CAD drawings that have been cross sectioned into thousands of layers. Sizes of printed objects run the gamut from approximately 16 to 4,000 cubic inches; however, Shanghai-based WinSun built huge machines to print house walls and trusses. See 3D printing materials.

Used for making prototypes as well as final products, 3D printing evolved from the "rapid prototyping" industry, pioneered by Chuck Hull of 3D Systems in the mid-1980s. It provides a faster and less costly alternative to machining (cutting, turning, grinding and drilling solid materials).

Concept, Prototype and Final Product
Capable of making a part from scratch in hours, or just minutes for small objects, 3D printing is used to create models to determine if a design meets the customer's expectations. It is also used to create prototypes of parts to test their form, fit and function with other parts in an assembly.

Laser sintering and electron beam melting technologies turned "rapid prototyping" into "rapid manufacturing," in which short runs of actual finished parts are made. These techniques are used to create products customized for humans as well, including hearing aids, dental crowns and medical implants.

3D printing is also used to make tooling molds and dies, as well as patterns for castings. Either the actual mold or the model to make the mold can be produced more quickly and economically than with conventional methods.

One Layer at a Time
All 3D printers are "additive fabrication" machines that build one layer after the other. The layers can be as thin as 1/1,000th of an inch or much thicker. The building material can be a liquid, powder or sheet material that is cured by heat, UV light, a chemical reaction or other method. The thickness exception is the cement mixture used by WinSun to print house walls in China. Following are the more common methods used to print 3D objects. See 3D printer, personal 3D printer, nanofactory and STL.

The Bible of 3D Printing

Known worldwide, Terry Wohlers' industry report describes the applications, players and technologies of 3D printing. For more information, visit www.wohlersassociates.com.

Stereolithography

In the mid-1980s, Chuck Hull pioneered the stereolithography apparatus (SLA) and ushered in rapid prototyping. Parts are built from a liquid photopolymer, and each layer is cured by a UV laser. When the excess resin and supports are removed, the whole part is cured. (Image courtesy of 3D Systems, Inc., www.3dsystems.com)

Laser Sintering

Laser sintering machines build parts from powdered plastics and metals that are heated by a laser. At the end of the job, the excess powder is removed and recycled for the next build. This metal part was created in a 3D Systems Sinterstation using the company's LaserForm resin. (Image courtesy of 3D Systems, Inc., www.3dsystems.com)

Fused Deposition Modeling (FDM)

FDM machines deposit a thermoplastic through a heated nozzle to form the layers, and the plastic solidifies. Developed by Scott Crump of Stratasys in the late 1980s, FDM is a popular technology for making prototypes. This is a close-up of the print head of a Stratasys FDM machine.

Electron Beam Melting (EBM)

Using an electron beam that melts metal powder a layer at a time in a vacuum chamber, EBM printers create titanium and cobalt chrome parts. Conventional machining may be required for finishing. These engine parts were made with an Arcam system. (Image courtesy of Arcam AB, www.arcam.com)

3D Printing in Colors

Z Corporation printers add color binders onto powdered, composite materials one layer at a time. This model was created as a single unit, and the excess powder was removed at the end. When any gear is rotated, all the others move. In 2011, the company was acquired by 3D Systems.

Jetting Liquid Polymer

Like inkjet printers, the Stratasys Objet piezoelectric print heads use thousands of nozzles to jet 16-micron layers of photopolymer that are immediately cured by UV light. The materials for the part and for the voids come from different nozzles. (Image courtesy of Stratasys Ltd., www.stratasys.com)

Medical Breakthroughs

By examining a plastic 3D model (top) derived from a CAT scan or MRI of the patient, surgeons can save hours at the operating table. 3D printers can also make custom parts like this cobalt chrome knee implant (bottom). (Images courtesy of Stratasys Ltd., www.stratasys.com and EOS GmbH, www.eos.info.)

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